1. Field of the Invention
The present invention relates to a method for obtaining a homogeneous dispersion of a pressurized gas in a high-viscosity liquid. More particularly, this invention relates to a method and associated apparatus for the controlled blending of a pressurized gas with a high viscosity liquid composition in a mixing chamber equipped with separate inlets for these two ingredients. The gas is distributed throughout resultant foamed mixture as bubbles with a uniformly small size and distribution that are consistent as a function of time. The viscous liquid is preferably a curable organosiloxane composition.
2. Background Information
Within the art of foam fabrication by mixing and reacting a high-viscosity liquid base agent with a liquid curing agent and the simultaneous evolution of a gas as a reaction by-product, the present applicants have filed U.S. patent application Ser. No. 08/173,312 on Dec. 23, 1993. The invention described in this application is a method for preparing foams from curable organosiloxane compositions. The objective of the method described in this application is the production of high-expansion-ratio foams having a uniform distribution of small cells. In accordance with the method described in this application, rapid bubble growth by the reaction gas is suppressed by the addition to the composition prior to curing of a small amount of inert gas into, for example, the base portion of the curable composition.
During their investigations into the fabrication of such homogeneous high-expansion-ratio foams, the inventors found that additional improvements in dispersing the small amount of inert gas that is blended into the viscous liquid were capable of yielding additional improvements in the quality of the cell dispersion in the cured foam.
Methods for mixing pressurized gases into high-viscosity liquids are already known from the production of whipped cream and urethane foams. However, as shown in the data plots that form part of the accompanying drawings it has been very difficult to obtain uniform gas-liquid mixtures when pressurized gases are blended into high-viscosity liquids.